Study On Preparation And Gas Bulging Micro-forming Of Electrodeposited Cu And Cu/Go Composites

With the rapid development of plastic micro-forming technology,Micro-bulging forming technology is widely used in the forming field due to its low production cost and high material utilization.However,the special forming law in the process of microplastic forming will have an adverse effect on the forming process.Therefore,it is of great significance to improve the plastic properties and forming stability of materials by reducing the grain size or adding reinforcing phases to obtain metal matrix composites.In this paper,pulse electrodeposition technology was used to prepare Cu and Cu/GO composites with different grain sizes by changing the content of additives in the electrodeposition solution,current density and the concentration of GO.The effects of grain size on the high temperature plasticity of Cu and Cu/GO composites were deeply analyzed by combining experimental research,morphology observation,microstructure texture and mechanical properties.The enhancement mechanism of GO as a reinforcing phase for Cu/GO composites was explored,and the optimum forming process parameters of different materials and the bursting law of micro-bulging were studied.Micro Cu and nano Cu were successfully prepared by pulse electrodeposition.The effects of current density and additive content on the grain size of copper substrate were studied.It is found that both increasing current density and introducing additives can effectively reduce the grain size of copper.Micro Cu and nano Cu prepare at a current density of 1.5 A/dm~2 and additive content of 0 ml/L and 4 ml/L,respectively,have the best surface morphology and mechanical properties.At room temperature,the tensile strength and elongation of micro Cu and nano Cu reach 220 MPa,300 MPa,and 11.2%,4.2%,respectively.At 600℃and a tensile speed of 0.6 mm/min,the elongation of nano Cu reaches 93%,which is more than 5 times that of micro Cu.The reinforcing phase GO with excellent performance was prepared by the improved Hummers method.It is found that the addition of GO can reduce the grain size of Cu/GO nanocomposites to 100～120 nm,GO can effectively improve the tensile strength and microhardness of the composites at room temperature.When the GO content is 0.09 g/L,the tensile strength and hardness of the composites reach the highest,which is 450 MPa and 155 HV,respectively.It is found that the strengthening mode of GO is mainly fine grain strengthening.In addition,it is found that GO can improve the high temperature elongation of Cu/GO composites.When the GO content is 0.05 g/L,the high temperature elongation of nano Cu/GO composites is 53%at 750℃.This is because GO can improve the high temperature stability of copper matrix composites and inhibit the growth of copper grains at high temperature.The gas bulging forming experiments of nano Cu and nano Cu/GO composites were carried out under the die with a pore size of 515μm.It is found that the optimum bulging temperature of nano Cu and nano Cu/GO is 600℃and 750℃,respectively.The maximum height-to-diameter ratios of the formed parts obtained by the gas expansion experiment of nano Cu and Cu/GO composites with a thickness about 55μm is 0.28 and 0.23,respectively.By observing the surface morphology and section metallographic diagram of the formed parts,it is found that the formed parts of different materials are hemispherical,and the thinning position mainly appears at the corner of the die and the top of the formed parts.The top of the formed part is the most serious thinning area,which is the main area of bursting.